A high flowability concrete and a method for producing the same

Abstract

The application relates to the technical field of concrete, in particular to high-fluidity concrete and a preparation method thereof, which comprises the following components in parts by weight: cement 300-400 parts; aggregate 800-1000 parts; fly ash 80-120 parts; modified functional material 1.2-1.8 parts; composite microcapsule 3.5-5.0 parts; water reducing agent 2-5 parts; and water 130-160 parts; wherein the modified functional material is fly ash carrier with a surface loaded nano modifier, the nano modifier is a core-shell structure nanoparticle, the inner core is silicon dioxide, and the surface is sequentially grafted with a polycarboxylic acid branched chain and a calcium-responsive phosphonic acid ligand; the modified functional material can make the nanoparticle loading rate reach 1.2-1.8% of the mass of the fly ash, and the distribution is uniform; the fly ash microbead not only acts as an admixture, but also serves as an efficient carrier of the nanoparticle, so that the uniform dispersion of the nanoparticle in the concrete is ensured.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to a high-flowability concrete and its preparation method. Background Technology

[0002] Regarding concrete materials, steel-shell immersed tubes have the following characteristics: First, they use highly fluid concrete, which can uniformly fill the compartmentalized steel shell structure without vibration; second, in addition to meeting the basic physical and mechanical properties of the concrete during long-term service, they must also maintain good cooperative deformation capacity with the steel shell; and third, the concrete should have good volume stability.

[0003] A steel-shell immersed tunnel is a composite structure consisting of a steel shell structure and concrete filling the steel shell structure. The steel shell structure is composed of hollow steel compartments of different sizes, with each compartment having an internal space of 0.5m. 3 ~13.5m 3 The internal steel compartment features L-shaped and flat steel ribs on both the upper and lower steel plates. A φ250mm concrete pouring port is located in the center of the top surface, with φ50mm vents around the perimeter. High-flowability concrete is poured into the steel compartment to evenly fill the gaps between the inner and outer steel shells, providing necessary weight support and protecting the inner steel shell, which serves as a permanent waterproofing measure, from corrosion. The steel-shell concrete primarily functions in terms of buoyancy resistance, stability, and mechanical balance, requiring excellent workability to fully fill the internal corners and edges of the steel shell.

[0004] However, high-flowability concrete currently faces two major technical bottlenecks in practical applications: First, the weak interfacial transition zone between aggregates and cement paste. Studies have shown that during the hardening process of concrete, an interfacial transition zone of about 30 μm thick forms on the surface of coarse aggregates. The innermost layer (the area <2.5 μm from the aggregate surface) has a porosity as high as 76.6%. This loose structure is due to the directional deposition of calcium hydroxide (CH) crystals caused by the "wall effect"—the aggregate surface acts as a "pore wall" to inhibit CH deposition, resulting in the innermost region exhibiting the "three lows" characteristic: significantly lower volume fractions of unreacted cement (8.2%), CSH gel (11.3%), and CH (3.9%) compared to the outer regions. The ITZ becomes the source of crack initiation and seepage channels, significantly reducing the mechanical properties and durability of concrete. The first issue is durability; the second is the risk of volume shrinkage and cracking caused by the heat of hydration: High-flowability concrete usually has a high amount of cementitious materials (510-540 kg / m³), resulting in concentrated heat release during hydration and a significant temperature rise. In closed structures such as steel-shell submerged tubes, the adiabatic temperature rise of concrete can reach 60-70℃. When the shrinkage deformation during the cooling stage is constrained by the steel shell, an interfacial gap of up to 1.4 mm will be generated. Existing technologies attempt to compensate for shrinkage by adding expansion agents (such as calcium sulfoaluminate) or porous materials (such as modified silica nanospheres), but there are two major limitations: First, the expansion agent is difficult to continue to play its role due to insufficient moisture in the later stage under low water-cement ratio conditions; second, the mechanical properties of porous aggregates (such as ceramics) are lower than those of quartz sand, and their introduction creates a weak link. In view of this, we propose a high-flowability concrete and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings mentioned in the background art and provide a high-flowability concrete and its preparation method.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A high-flowability concrete comprises the following components in parts by weight:

[0008] Cement: 300-400 parts;

[0009] Aggregate: 800-1000 parts;

[0010] Fly ash: 80-120 parts;

[0011] Modified functional materials: 1.2–1.8 parts;

[0012] Composite microcapsules: 3.5–5.0 parts;

[0013] Water-reducing agent: 2-5 parts;

[0014] Water: 130-160 parts;

[0015] Among them, the modified functional material is a fly ash carrier with a surface-loaded nano-modifier. The nano-modifier is a core-shell structured nanoparticle with a core of silicon dioxide and a surface sequentially grafted with polycarboxylic acid branches and calcium-responsive phosphonic acid ligands.

[0016] Preferably, the composite microcapsule is a mixture of triple composite phase change microcapsules and double-coated expansion cores in a mass ratio of 2:1.

[0017] Preferably, the preparation steps of the modified functional material are as follows:

[0018] Step 1: Preheat fly ash microspheres with a particle size ≤20μm and a silica content ≥60% to 120~150℃;

[0019] Step 2: Spray a suspension of core-shell structured nanoparticles at an atomization pressure of 0.3~0.5MPa;

[0020] Step 3: Heat-set for 5-8 minutes to achieve a core-shell structure nanoparticle loading rate of 1.2-1.8% of the fly ash mass, thus obtaining the modified functional material.

[0021] Preferably, the structure of the triple composite phase change microcapsule in the composite microcapsule is as follows: the core is a eutectic mixture of lauric acid and stearic acid; the middle layer is a paraffin-ethylene vinyl acetate copolymer; and the outer layer is a poly(N-isopropylacrylamide) thermosensitive film.

[0022] Preferably, the structure of the double-coated expansion core in the composite microcapsule is as follows: the core is a mixture of calcium sulfoaluminate and magnesium oxide, doped with highly absorbent resin microparticles; the first coating layer is a pH-responsive methacrylic acid copolymer; and the second coating layer is a hydroxypropyl methylcellulose water-soluble film.

[0023] A method for preparing highly fluid concrete includes the following steps:

[0024] Step 1: Mix the aggregate and water according to the weight parts, stir evenly, and obtain a premixed composition;

[0025] Step 2: Then add cement, fly ash, modified functional materials and remaining water to the premixed composition, stir evenly, and obtain the base concrete;

[0026] Step 3: Add the water-reducing agent and composite microcapsules to the base concrete and stir for 60 seconds until the slump spread reaches 700±25mm to obtain high-flowability concrete.

[0027] Preferably, the modified functional material is added in step two 20-40 seconds after stirring begins, at which time the pH of the slurry is 10-11.

[0028] Preferably, the conditions for adding the composite microcapsules in step three are: concrete temperature ≤ 40℃ and stirring speed ≤ 200 rpm.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. This invention uses modified functional materials with silica nanospheres as the core, polycarboxylic acid branches grafted onto the surface through silane coupling agents to form an intermediate layer, and calcium-responsive organic ligands, such as phosphonic acid groups, anchored in the outermost layer. This special structure enables it to have "intelligent migration" and "in-situ activation" functions. The hydrophilic polycarboxylic acid branches ensure that the particles are uniformly dispersed in the concrete mixture, while the hydrophobic phosphonic acid groups give them the ability to migrate to the aggregate surface. Furthermore, the modified functional materials of this application can achieve a nanoparticle loading rate of 1.2-1.8% of the fly ash mass, and the distribution is uniform. Here, fly ash microspheres not only serve as an admixture, but also as an efficient carrier for nanoparticles, ensuring their uniform dispersion in concrete.

[0031] 2. During the concrete mixing process of the present invention, the nanoparticles released by the modified fly ash microspheres spontaneously migrate to the aggregate-slurry interface region due to the polarity difference between their hydrophobic and hydrophilic ends. When they approach the aggregate surface, the phosphonic acid groups undergo a coordination reaction with the calcium ions on the aggregate surface to form a stable "Ca-OP" chemical bond, thereby achieving firm anchoring of the nanoparticles on the aggregate surface.

[0032] 3. This invention utilizes added composite microcapsules. When the internal temperature of the concrete reaches 50-55℃, typically occurring 10-24 hours after pouring, the outer membrane of the triple composite phase change microcapsules ruptures, releasing the phase change material. This material absorbs heat through a solid-liquid phase change, with a phase change enthalpy ≥180J / g. This process can slow the temperature rise rate by up to 40%, delaying the temperature peak by 6-8 hours and reducing the peak temperature by 8-12℃. More importantly, molten organic acid molecules can penetrate into the CSH gel layers, exerting a "molecular lubrication" effect, reducing the shrinkage strain of the concrete during the cooling phase by 35-50%. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The present invention will describe the above technical solution in detail through the following embodiments:

[0035] Example 1

[0036] A high-flowability concrete comprises the following components in parts by weight:

[0037] Cement: 350 parts;

[0038] Aggregate: 900 parts;

[0039] Fly ash: 90 parts;

[0040] Modified functional materials: 1.2 parts;

[0041] Composite microcapsules: 3.5 parts;

[0042] Water-reducing agent: 3 parts;

[0043] Water: 130 portions;

[0044] Among them, the modified functional material is a fly ash carrier with a surface-loaded nano-modifier. The nano-modifier is a core-shell structured nanoparticle with a core of silica (particle size ≤500nm, specific surface area ≥5.6×10³m² / kg) and a surface sequentially grafted with polycarboxylic acid branches and calcium-responsive phosphonic acid ligands.

[0045] The composite microcapsule is a mixture of triple composite phase change microcapsules and double-coated expansion cores in a mass ratio of 2:1. The preparation method of the composite microcapsule is as follows: the triple composite phase change microcapsules and double-coated expansion cores are put into a V-type mixer in a mass ratio of 2:1, 0.5wt% nano silica flow aid is added, the speed is 30 rpm, and the mixture is mixed for 30 min until uniform.

[0046] The specific steps for preparing the modified functional material are as follows:

[0047] Step 1: Preheat fly ash microspheres with a particle size ≤20μm and a silica content ≥60% to 120~150℃;

[0048] Step 2: Spray a suspension of core-shell structured nanoparticles at an atomization pressure of 0.3~0.5MPa;

[0049] Step 3: Heat-set for 5-8 minutes to achieve a core-shell structure nanoparticle loading rate of 1.2-1.8% of the fly ash mass, thus obtaining the modified functional material.

[0050] It should be noted that during the concrete mixing process, the nanoparticles released by the modified fly ash microspheres spontaneously migrate to the aggregate-slurry interface region due to the polarity difference between their hydrophobic and hydrophilic ends. When they approach the aggregate surface, the phosphonic acid groups undergo a coordination reaction with the calcium ions on the aggregate surface to form a stable "Ca-OP" chemical bond, thereby achieving a firm anchoring of the nanoparticles on the aggregate surface.

[0051] Nanoscale nucleation template effect: Nanoparticles anchored to the aggregate surface become heterogeneous nucleation sites for hydration products. This effect can increase the deposition rate of CSH gel in the ITZ region by more than 40%, significantly improving the innermost layer structure: reducing the porosity at 0.5 μm from 76.6% to 52.3%, and increasing the CSH gel volume fraction from 11.3% to 28.7%. Simultaneously, the polycarboxylic acid branches on the nanoparticle surface can adsorb free... This locally increases ion concentration and accelerates the deposition of hydration products.

[0052] Crystal growth regulation: Organic ligands on the surface of nanoparticles can regulate the morphology of calcium hydroxide (CH) crystals, transforming them from plate-like growth parallel to the interface to fibrous growth with vertical orientation. This transformation changes the microcrack propagation path in the ITZ region from a straight line to a serrated shape, significantly increasing the crack propagation energy. The energy required for microcrack propagation in the modified ITZ is increased by 2.3 times, and the interfacial bonding strength is increased by more than 35%.

[0053] The structure of the triple composite phase change microcapsule in the composite microcapsule is as follows: the core is a eutectic mixture of lauric acid and stearic acid with a phase change temperature of 50~55℃; the middle layer is a paraffin-ethylene vinyl acetate copolymer; and the outer layer is a poly(N-isopropylacrylamide) thermosensitive film with a critical dissolution temperature of 55℃.

[0054] It should be noted that the preparation method of the triple composite phase change microcapsules is as follows: Lauric acid and stearic acid are mixed at a mass ratio of 6:4, stirred in a water bath at 70°C until a transparent liquid is formed, and a phase change enthalpy enhancer, such as 0.5wt% nano boron nitride, is added. The mixture is ultrasonically dispersed for 30 min, and then an O / W emulsion is prepared: oil phase: molten phase change core + paraffin-EVA copolymer, aqueous phase: 2wt% polyvinyl alcohol + 0.1wt% sodium dodecyl sulfate. The mixture is then emulsified under high-speed shear at 12000 rpm for 10 min to form emulsion droplets with a particle size of 50-100 μm. The droplets are then rapidly cooled and solidified in an ice-water bath, filtered, and dried to obtain phase change core@paraffin-EVA microspheres. The microspheres are dispersed in an aqueous solution containing 1wt% NIPAM monomer, and a crosslinking agent N,N'-methylenebisacrylamide is added. Nitrogen gas is then introduced, and 0.3wt% ammonium persulfate initiator is added dropwise. The mixture is reacted at 40°C for 6 h, centrifuged, washed, and vacuum dried at 45°C to obtain triple composite phase change microcapsules.

[0055] It needs to be explained that the triple composite phase change microcapsule adopts a composite structure of "inorganic phase change core + organic phase change shell + thermally triggered release membrane": the core is a eutectic mixture of lauric acid and stearic acid with a phase change temperature of 50-55℃, the middle layer is a paraffin-ethylene vinyl acetate copolymer, and the outer layer is wrapped with a thermosensitive polymer microcapsule with poly(N-isopropylacrylamide) as the substrate and a critical dissolution temperature of 55℃. This design enables the triple composite phase change microcapsule to undergo a phase change when the concrete temperature reaches 55℃. The outer polymer membrane changes from hydrophilic to hydrophobic, generating microcracks and releasing the core phase change material.

[0056] When the internal temperature of concrete reaches 50-55℃, usually 10-24 hours after pouring, the outer membrane of the microcapsules ruptures and releases phase change material. It absorbs heat through solid-liquid phase change with a phase change enthalpy ≥180J / g. This process can slow down the temperature rise rate by up to 40%, postpone the temperature peak by 6-8 hours, and reduce the peak temperature by 8-12℃. More importantly, molten organic acid molecules can penetrate into the CSH gel layer and exert a "molecular lubrication" effect, which reduces the shrinkage strain of concrete during the cooling stage by 35-50%.

[0057] The structure of the double-coated expansion core in the composite microcapsule is as follows: the core is a mixture of calcium sulfoaluminate and magnesium oxide in a mass ratio of 3:1, and is doped with highly absorbent resin microparticles; the first coating layer is a pH-responsive methacrylic acid copolymer with a solubility pH ≥ 12.5; and the second coating layer is a hydroxypropyl methylcellulose water-soluble film.

[0058] It should be noted that the preparation method of the double-coated expansion core is as follows: Calcium sulfoaluminate and magnesium oxide are mixed and ground at a ratio of 3:1 until D50 = 15 μm. Pre-swollen SAP microparticles with a particle size of 100-150 μm and a water absorption rate of 200 times are added, along with 2wt% hydroxypropyl cellulose. Then, fluidized bed spray granulation is performed at an inlet air temperature of 60℃ and an atomization pressure of 0.2 MPa to obtain particles with a particle size of 200-300 μm. Then, dimethylaminoethyl methacrylate: methacrylic acid = 7:3 (molar ratio) is dissolved in an ethanol / water (4:1) mixed solvent with a solid content of 12%. This is then coated using a bottom-spray fluidized bed coating at an inlet air temperature of 45℃ and an atomization pressure of 0.15 MPa, resulting in a coating weight gain of 8% and a film thickness of 5-8 μm. Finally, 5wt% hydroxypropyl cellulose is used. HPMC aqueous solution was used as the coating solution for secondary coating in the same equipment. The inlet air temperature was 50℃, the atomization pressure was 0.1MPa, the coating weight gain was 7%, the film thickness was 10-15μm, and finally it was cured at 40℃ for 24h to obtain a double-coated expansion core.

[0059] It should be explained that the double-coated expansion core uses calcium sulfoaluminate and magnesium oxide as the expansion source core in a mass ratio of 3:1. The first layer is coated with a pH-responsive polymer (dimethylaminoethyl methacrylate-methacrylic acid copolymer), and the second layer is coated with a water-soluble delayed membrane (hydroxypropyl methylcellulose, HPMC). This design gives the expansion components a dual release mechanism. When the pH of the concrete pore fluid is >12.5, usually during the cement hydration acceleration period, the pH-responsive layer dissolves and releases part of the CSA; the remaining components are released after the HPMC membrane slowly dissolves in water, about 24-48 hours later, realizing the phased triggering of the expansion effect.

[0060] To address the issue of expansion agent failure due to water shortage under low water-cement ratio conditions, superabsorbent polymer (SAP) microparticles are added to the expansion core. These SAP microparticles pre-absorb water equivalent to 200 times their own weight, providing a local water source after the expansion agent is released, ensuring the expansion reaction continues. This design can improve expansion efficiency by 80%, achieving an expansion strain of 60-90 με in a formulation with a cementitious material dosage of 540 kg / m³, effectively compensating for cold shrinkage.

[0061] A method for preparing highly fluid concrete includes the following steps:

[0062] Step 1: Mix the aggregate and water according to the weight parts, stir evenly, and obtain a premixed composition;

[0063] Step 2: Then add cement, fly ash, modified functional materials and remaining water to the premixed composition, stir evenly, and obtain the base concrete;

[0064] Step 3: Add the water-reducing agent and composite microcapsules to the base concrete and stir for 60 seconds until the slump spread reaches 700±25mm to obtain high-flowability concrete.

[0065] In step two, the modified functional material is added 20-40 seconds after stirring begins, at which point the slurry pH is 10-11.

[0066] The conditions for adding the composite microcapsules in step three are: concrete temperature ≤ 40℃ and stirring speed ≤ 200 rpm.

[0067] Example 2

[0068] The only difference between this embodiment and Embodiment 1 is that 1.4 parts of modified functional material and 4 parts of composite microcapsules are added in this embodiment, while all other conditions are the same.

[0069] Example 3

[0070] The only difference between this embodiment and Embodiment 1 is that 1.6 parts of modified functional material and 4.5 parts of composite microcapsules are added in this embodiment, while all other conditions are the same.

[0071] Example 4

[0072] The only difference between this embodiment and Embodiment 1 is that 1.8 parts of modified functional material and 5 parts of composite microcapsules are added in this embodiment, while all other conditions are the same.

[0073] Comparative Example 1

[0074] The only difference between this comparative example and Example 1 is that no modified functional materials are added in this comparative example, while all other conditions are the same.

[0075] Comparative Example 2

[0076] The only difference between this comparative example and Example 1 is that no composite microcapsules are added in this comparative example, while all other conditions are the same.

[0077] Comparative Example 3

[0078] The only difference between this comparative example and Example 1 is that the mass ratio of the triple composite phase change microcapsules to the double-coated expansion core in this comparative example is 1:1, while all other conditions are the same.

[0079] Comparative Example 4

[0080] The only difference between this comparative example and Example 1 is that the mass ratio of the triple composite phase change microcapsule to the double-coated expansion core in this comparative example is 3:1, while all other conditions are the same.

[0081] Performance testing

[0082] The high-flowability concrete obtained in Examples 1-4 and the high-flowability concrete obtained in Comparative Examples 1-4 were selected as samples for testing;

[0083] Collapse expansion (GB / T 50080-2016)

[0084] Procedure: Fill the slump cone with concrete, lift it vertically and measure the expansion diameter. Control target: 700±25mm.

[0085] Slump cone evacuation time (ASTM C1611 / C1611M)

[0086] Procedure: Record the time it takes for the concrete in the inverted slump cone to completely empty, reflecting the self-compacting performance (≤12s is acceptable).

[0087] Compressive strength (GB / T 50081-2019)

[0088] Process: Mold 100mm cube specimens, cure for 7 days / 28 days and then test.

[0089] Interfacial bond strength (DL / T 5150-2017)

[0090] Procedure: Prepare "concrete-steel plate" composite specimens and test the interfacial adhesion using the pull-out method.

[0091] Chloride ion diffusion coefficient (GB / T 50082-2009)

[0092] Procedure: Immerse 28-day-old specimens in NaCl solution, apply 60V voltage for 6 hours, and measure the chloride ion penetration depth.

[0093] 28-day drying shrinkage (GB / T 50082-2009)

[0094] Procedure: Measure the shrinkage deformation of a 100×100×515mm prism specimen under constant temperature and humidity (20℃, 60%RH).

[0095] Adiabatic temperature rise (GB / T 50496-2019)

[0096] Procedure: Place the concrete in an adiabatic temperature rise meter and record the internal temperature change over 72 hours (thermocouple buried at 1 / 2 section depth).

[0097] Expansion strain (JC / T 603-2004)

[0098] Procedure: Insert vibrating wire strain gauges and record the expansion deformation within 7 days after pouring.

[0099] The specific data are shown in Tables 1 and 2 below:

[0100]

[0101] Table 1

[0102]

[0103] Table 2

[0104] As shown in the table above, when the amount of modified material added is ≥1.4 parts, the interfacial bonding strength is increased by more than 35%, compared to only 2.41 MPa in Comparative Example 1 and 3.92 MPa in Example 3. Furthermore, the chloride ion diffusion coefficient is reduced by 40%-50%, demonstrating a significant improvement in the density of the ITZ region.

[0105] Comparing Example 1 and Comparative Example 2, it can be seen that the adiabatic temperature peak decreased by 9.6°C and the drying shrinkage decreased by 37% after adding the composite microcapsules, while Comparative Example 2 had no expansion compensation.

[0106] Comparing Comparative Examples 3-4, it can be seen that in Example 1, when the mass ratio of the triple composite phase change microcapsules to the double-coated expansion core is 2:1, the balance between temperature rise suppression and expansion compensation is optimal, with a temperature peak of 58.2℃ and an expansion of 62με. In Comparative Example 3, when the mass ratio of the triple composite phase change microcapsules to the double-coated expansion core is 1:1, excessive expansion leads to a decrease in strength, and insufficient expansion in Comparative Example 3 cannot compensate for shrinkage.

[0107] In summary, Example 3 exhibits the best overall performance.

[0108] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A high flowability concrete, characterized in that: Comprise the following components by weight: Cement: 300-400 parts; Aggregate: 800-1000 parts; Fly ash: 80-120 parts; Modified functional material: 1.2-1.8 parts; Composite microcapsule: 3.5-5.0 parts; Water reducing agent: 2-5 parts; Water: 130-160 parts; The modified functional material is a fly ash carrier loaded with a nano modifier on the surface, and the nano modifier is a core-shell structure nanoparticle, the inner core of which is silicon dioxide, and the surface of which is sequentially grafted with a polycarboxylic acid branched chain and a calcium-responsive phosphonic acid ligand. The composite microcapsule is a mixture of a triple-composite phase change microcapsule and a double-coated swelling core, with a mass ratio of 2:

1. The structure of the triple-composite phase change microcapsule in the composite microcapsule is as follows: the inner core is a eutectic mixture of lauric acid and stearic acid; the intermediate layer is a paraffin-ethylene vinyl acetate copolymer; and the outer layer is a poly-N-isopropyl acrylamide temperature-sensitive film. The structure of the double-coated swelling core in the composite microcapsule is as follows: the core is a mixture of calcium sulfoaluminate and magnesium oxide, with high water-absorbing resin particles added; the first coating layer is a pH-responsive methacrylic acid copolymer; and the second coating layer is a hydroxypropyl methylcellulose water-soluble film.

2. The high flowability concrete according to claim 1, characterized in that: The preparation steps of the modified functional material are as follows: Step one: preheat fly ash beads with a particle size ≤20 μm and a silicon dioxide content ≥60% to 120-150°C; Step two: spray a core-shell structure nanoparticle suspension under a 0.3-0.5 MPa atomization pressure; Step three: heat and solidify for 5-8 minutes to achieve a core-shell structure nanoparticle loading rate of 1.2-1.8% of the mass of the fly ash, thereby obtaining the modified functional material.

3. A method for the production of a high fluidity concrete, suitable for use in a high fluidity concrete according to any one of claims 1-2, c h a r a c t e r i s e d in that: The method comprises the following steps: Step one: mix the aggregate and water according to the weight parts, and stir until uniform to obtain a premixed composition; Step two: then add cement, fly ash, modified functional material, and the remaining water to the premixed composition, and stir until uniform to obtain a basic concrete; Step three: add a water reducing agent and a composite microcapsule to the basic concrete, and stir for 60 s until the slump spread reaches 700 ± 25 mm, thereby obtaining a high-fluidity concrete.

4. The method of preparing high flowability concrete according to claim 3, characterized by: The modified functional material is added in step two after 20-40 s of stirring, at which time the slurry pH is 10-11.

5. The method of preparing high flowability concrete according to claim 3, wherein: The composite microcapsule is added in step three under the following conditions: concrete temperature ≤40°C, and stirring speed ≤200 rpm.

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